EXAMPLE 3.16 Effects of TV Advertising
What are the effects of repeated exposure to an advertising message? The answer may depend both on the length of the ad and on how often it is repeated. An experiment investigates this question using undergraduate students as subjects. All subjects view a 40-minute television program that includes ads for a digital camera. Some subjects see a 30-second commercial; others, a 90-second version. The same commercial is repeated one, three, or five times during the program. After viewing, all of the subjects answer questions about their recall of the ad, their attitude toward the camera, and their intention to purchase it. These are the response variables.21
This experiment has two factors: length of the commercial, with two levels; and repetitions, with three levels. All possible combinations of the factor levels form six treatment combinations. Figure 3.4 shows the layout of these treatments.
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